Washington is in “close contact” with Ankara over the assault launched by American-backed Kurdish-Arab forces on the Islamic State group’s bastion Raqa in Syria, a senior US official said. “We are in close close contact with our Turkish allies and that is why the chairman of joint chiefs is in Ankara today,” Brett McGurk, President Barack Obama’s envoy to the US-led coalition battling the jihadists, told a news conference in the Jordanian capital Amman.

“We want this to be as coordinated as possible, recognising that there will be a mix of forces on the field and that many of those forces of course do not see eye to eye, but they do share a very common and still very lethal enemy,” he said of IS.

The chairman of the US joint chiefs of staff, General Joseph Dunford, arrived Monday in Ankara on a previously unannounced visit and was to meet his Turkish counterpart Hulusi Akar, the Turkish army said earlier, without elaborating. The US-backed Kurdish-Arab Syrian Democratic Forces (SDF) leading the fight to retake Raqa from the jihadists said earlier that Washington had agreed Turkey would play no role in the offensive.

Ankara had previously expressed alarm that the SDF were dominated by the Kurdish Peoples’ Protection Units (YPG) militia which it considers an offshoot of the Kurdistan Workers’ Party (PKK) that has waged an insurgency against Turkey for more than three decades.

“It is a complex environment in Syria to say the least, but we are constantly in touch with all the different players, and I think in terms of the phasing of the overall Raqa campaign we have a fairly good understanding of what is to come,” said McGurk.